Orthostatic intolerance, also commonly referred to as “suspension trauma”, may include symptoms such as light-headedness, breathlessness, palpitations, tremulousness, poor concentration, fatigue, nausea, dizziness, headache, sweating, paleness, increased or unusually low heart rate, unusually low blood pressure, loss of vision, weakness, and faintness. While in a sedentary position, blood can accumulate in the veins, commonly referred to as “venous pooling,” and cause orthostatic intolerance. Venous pooling typically occurs in the legs due to gravity and a lack of movement, and an accumulation of blood in the legs reduces the amount of blood in circulation throughout the rest of the body. The body reacts by speeding up the heart rate in an attempt to maintain sufficient blood flow to the brain. If the blood supply is sufficiently reduced, this reaction will not be effective. The body will abruptly slow the heart rate and the blood pressure will diminish in the arteries. During severe venous pooling, the reduction in quantity and/or quality of oxygen content in the blood flowing to the brain will cause one or more of the above-mentioned symptoms. This reduction of oxygen in the blood can also have an effect on other vital organs such as the kidneys, which may result in renal failure. If these conditions continue, they may be fatal.
Orthostatic intolerance may be experienced by workers using fall protection systems including full body harnesses. After a fall, a worker is suspended by the dorsal D-ring of the full body harness, and the worker is left suspended in a relatively vertical/upright position by the fall protection system until rescued. The worker may remain suspended in the full body harness for a length of time, and the sustained immobility may lead to a state of unconsciousness and/or any of the other above-mentioned symptoms. Depending upon the length of time the suspended worker is unconscious and/or immobile and depending upon the level of venous pooling, the resulting orthostatic intolerance may possibly lead to death. While not common, such fatalities are often referred to as “harness induced pathology”.
Unconscious and/or immobile workers suspended in their harnesses will not be able to move their legs and will not fall into a horizontal position as they would if they were standing. While in the relatively vertical/upright position, venous pooling is more likely to occur and cause orthostatic intolerance, especially if the suspended worker is left in such a position for a length of time. If the worker is not rescued timely, in less than 30 minutes, venous pooling and orthostatic intolerance could result in serious injury or even death as the brain, the kidneys, and other organs are deprived of oxygen. Care must be taken during the rescue because moving the worker quickly into a horizontal position could cause cardiac arrest due to the abrupt increase in blood flow to the heart.
OSHA has suggested that footholds may be used to alleviate pressure on the workers' legs and provide support for “muscle pumping” to activate the leg muscles and reduce the risk of venous pooling. Therefore, a full body harness incorporating such a foothold is desired to reduce the risk of suspension trauma.